Take a step back to understand muscle behaviour in chronic low back pain

There is a popular belief that chronic non specific low back pain (CNSLBP) patients need to have higher activation of their trunk muscles during simple functional tasks in order to stabilize their spine. Changes in pain and disability, however, do not seem to be mediated by deep muscle activity changes targeted by some exercise interventions during clinical trials, and, further, stabilization exercises have not been shown to be superior to general exercises[1­–4].  Perhaps, it is time to take a step back and try to understand the mechanisms that underpin maladaptive functional behaviour of patients with CNSLBP and their relationship with other contributing factors.

Recent research has focused on the superficial trunk muscle activity of patients with low back pain and its relationship to cognitive and emotional factors. Ross et al. showed that individuals with a high level of pain catastrophizing tended to stabilize their spines during a repetitive unloaded spine flexion/extension movement after a noxious stimulation to induce low back pain [5]. Pakzad et al. found a significant correlation between trunk muscle activation amplitude and pain catastrophizing in patients with CNSLBP during walking on a treadmill [6]. A systematic review showed higher activation in the back and abdominal muscles and decreased trunk mobility during gait [7].

It remains unknown whether this maladaptive behaviour is generalized across different functional tasks and whether pain-related psychosocial factors are correlated with back muscle activity. Thus, the aims of our study [8] were (1) to analyse the activity of the back muscles during five functional tasks and (2) to test whether the electromyographic activity of the back muscles is correlated with kinesiophobia scores and scores on the Örebro Questionnaire in CNSLBP patients.

Forty patients with CNSLBP and 40 asymptomatic participants who have never experienced disability caused by LBP were enrolled in this study. The patients reported experiencing low back pain for more than three months, were between 18 and 60 years old and were referred by a physician. Electromyographic activity of the lumbar longissimus, iliocostal and multifidus was recorded simultaneously using an 8-channel amplifier (model 810, EMG System, SP, Brazil).

All participants were asked to perform five functional tasks: picking up an object from the ground; placing an object on the ground; sitting down; standing up; and climbing up a stair.

Patients showed an increase in back muscle activity regardless of the type of functional task (F4,308 = 7.921, p < 0.001, η2 = 0.049). Although some recent studies have shown a link between psychosocial factors and trunk muscle activity, we did not find a significant correlation – even though the levels of kinesiophobia and the scores of the Örebro Questionnaire of the patients were very high. This could have been caused by a ceiling effect, precluding a distinction between those who had low or high levels of kinesiophobia and a low or high score on the Örebro Questionnaire.

Our findings suggest that stimulating the muscle activity of CNSLBP patients may be counterproductive. Randomised clinical trials are necessary to test exercise interventions with the aim of relaxing the back muscles during activities such as sitting and standing, climbing stairs and picking up and placing an object on the ground.

About Ney Meziat-Filho

Ney is an Assistant Professor of the Postgraduate Program in Rehabilitation Sciences at Centro Universitário Augusto Motta (UNISUAM), Rio de Janeiro, Brazil. In addition to his teaching and research at UNISUAM, he works in clinical practice as a Musculoskeletal Physiotherapist. Ney’s research interests include epidemiological and clinical aspects of low back and neck pain. He has been coordinating two clinical trials with the aim of investigating the efficacy of Cognitive Functional Therapy (CFT) for chronic low back pain. Ney has qualifications in Epidemiology and completed his PhD in 2014 at the Institute of Social Medicine of the Rio de Janeiro State University.

References

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[5] Ross GB, Sheahan PJ, Mahoney B, Gurd BJ, Hodges PW, Graham RB. Pain catastrophizing moderates changes in spinal control in response to noxiously in-duced low back pain. J. Biomech. (2017), http://dx.doi.org/10.1016/j.jbiomech. 2017.04.010.

[6] Pakzad M, Fung J, Preuss R. Pain catastrophizing and trunk muscle activation during walking in patients with chronic low back pain. Gait Posture 49 (2016) 73–77.

[7] Ghamkhar L, Kahlaee AH. Trunk muscles activation pattern during walking in subjects with and without chronic low back pain: a systematic review. PMR 7 (5) (2015) 519–526, http://dx.doi.org/10.1016/j.pmrj.2015.01.013.

[8] Maicom Lima, Arthur Sá Ferreira, Felipe José Jandre Reis, Vanessa Paes, Ney Meziat-Filho. Chronic low back pain and back muscle activity during functional tasks. Gait and Posture 61, (2018), 250-256.